2:Here I made a quick comparison at 100% brightness on both. Contrast on BMVA at 50%.Scene exposure was right, just slightly over-exposed. Mostly bright, with some darker areas, white wall, sky and clouds. So, both monitors have almost identical brightness, but I think the UM46 was slightly easier to see.

3:Then I made a "zoomed in" comparison, in an area, that was slightly over-exposed. It revealed, that the BMVA 4K has less dynamic range, than the UM46 monitor. As you can see, the edge detail on the white wall is lost on the BMVA, while still visible on the UM46. Also you can see that difference in the sky / clouds area.